1. Field of the Invention
This invention relates to medical devices and in particular a multi-pole electrode catheter and method for endocardial mapping and ablation. A single catheter is capable both of mapping the atrial and ventricular heart chambers, as well as ablating foci or bypass tracts that cause dysrhythmias.
2. Description of the Prior Art
In the treatment of cardiac dysrhythmias, nonsurgical procedures such a management with drugs are favored. However, some dysrhythmias of the heart are not treatable with drugs. In addition, some patients of advanced age or illness may not tolerate invasive surgery to excise tachycardias which cause dysrhythmias.
Endocardial mapping is a technique that typically involves percutaneously introducing an electrode catheter into the patient. The electrode catheter is passed through a blood vessel, the aorta and thence into an endocardial site such as the atrium or ventricle of the heart. A tachycardia is induced and a continuous, simultaneous recording made with a multichannel recorder while the electrode catheter is moved to different endocardial positions. When a tachycardial foci is located as indicated in an electrocardiogram recording, it is marked by means of a fluoroscopic image.
Under earlier techniques, the mapping catheter would be withdrawn and replaced by an ablation catheter. The ablation catheter contained one or more electrodes for delivering a controlled burst of energy, of the order of 100 joules or so, to the foci. The foci would be ablated and the patient monitored for a period of time to ensure that there would be no reoccurrence of the dysrhythmia. This removal of the mapping catheter was both time-consuming as well as subject to inherent inaccuracies. This is because the location of the tachycardial foci could not always be precisely relocated by using the fluoroscope.
As a result, catheters have been developed for the location and ablation of such tachycardias that perform both the mapping and ablation functions with the same catheter. One such mapping and ablation catheter is a hexipolar catheter made by the United States Catheter and Instrument Corporation. This prior art device has a series of six electrode rings in alternating 2 and 5 mm distances along an elongated woven Dacron surface. Bipolar electrograms are used to determine the site for ablation.
Problems with this and other prior art devices are manifest. First, the area of mapping is fairly large and imprecise. That is, the foci can only be found within about 10-12 cm.sup.2 and at best only about 2-3 cm of the site.
Corollary to this is that the area ablated must be unduly large since the site of the foci is only known to this precision. The prior art electrode catheters also deliver the ablative charge over a wider than necessary area. This causes tissue and cell damage beyond the foci.